Switching payroll software in Senegal: a 6-step migration guide

Changing payroll tool is daunting for a good reason: a wrong payslip is noticed immediately, and employee trust is slow to repair. Yet a well-run migration takes a few days of work, not weeks, provided you respect two principles: carry over the year's cumulative figures, and never switch without having compared a full month.

This sheet describes the method we apply at Izi Paie, but it holds for any change of tool.

Choosing the right moment

Not all months are equal.

January remains the best moment. Annual counters start from zero: cumulative taxable gross, tax already withheld, leave accrued. There is nothing to carry over mid-course, and the first payroll on the new tool is also the first payroll of the financial year.

July is the second-best choice. You carry over six months of cumulative figures, which stays manageable, and you still have six months to settle before the December adjustment.

Two periods to avoid. December, because it is the month of the annual tax adjustment, the most complex of the year. And any month when a heavy deadline falls in parallel: an inspection, an audit, an accounting close, a wave of hires.

If you are starting your business or have no tool at all yet, the question does not arise: start whenever you like, there is nothing to carry over.

Step 1: list what you need to retrieve

Before asking your current provider for anything, list precisely what you will need. Most migrations go off course because one item is missing and has to be chased.

For each employee

• Full identity: surname, first name, date of birth, identity document number, family situation, number of dependent children.
• Registration numbers: IPRES, CSS, and IPM where applicable.
• Tax situation: tax parts, TRIMF parts, any exemptions.
• Contract: employee number, hire date, contract type, end date for fixed-term contracts, position, professional category.
• Seniority date, which is not always the hire date. Seniority credited at hiring changes the seniority bonus and the severance payment. It is the piece of information most often lost during a migration.
• Pay: base salary, above-scale supplement, permanent bonuses and allowances with their social and tax treatment.
• Bank details.

For the company

• Applicable collective agreement, and the classification grid if you use one.
• Work accident rate assigned by the CSS, which depends on your activity.
• Your IPM parameters: overall rate, employer and employee split, ceiling.

For the history

• The last twelve months of payslips as PDFs, to archive.
• The current year's cumulative figures, detailed in step 3.
• Salary advances still being repaid, with the outstanding balance.
• Leave accrued and taken.

Step 2: clean the data before transferring it

A migration is the only occasion in the year when every record passes under someone's eyes. Take advantage of it, because a dirty file stays dirty once imported.

The checks that pay off most:

• Departed employees still present in the file. They have no place in the new tool.
• Duplicate employee numbers, common when two people have been entering data in parallel.
• Outdated tax parts: a marriage, a birth or a divorce never passed on. The employee has been paying too much or too little tax for months.
• Missing seniority dates, silently replaced by the hire date.
• Bonuses that no longer apply, paid out of habit.

Allow half a day for around thirty employees. It is the best investment of the whole migration.

Step 3: carry over the current year's cumulative figures

This is the step that failed migrations forget, and the only one that is costly.

In Senegal, the income tax withheld each month is a projection: annual tax is calculated from the month's income, and one twelfth of it is withheld. In December the employer adjusts: they recalculate the tax actually due on the year's real income, and correct the final withholding accordingly. An employee who received an exceptional bonus in July has overpaid for six months; the adjustment returns the difference.

This adjustment is only possible if the new tool knows, for each employee:

• the cumulative taxable gross since January;
• the cumulative income tax already withheld;
• the cumulative TRIMF already withheld.

Without these three figures, December's adjustment will be wrong for everyone. If you migrate in January, the problem disappears: the cumulative figures are zero.

Carry over the leave accrued and taken at the same time, along with the balance of salary advances in progress. An advance repayable in ten instalments of which six have been deducted must resume at the seventh, not the first.

Step 4: run one month in parallel

Never switch directly. Choose a month already paid, preferably the previous one, and redo it in full in the new tool with the same variable inputs: bonuses, overtime, absences, leave.

You end up with two sets of payslips for the same month: the old one, which is authoritative, and the new one, which must match it. This parallel month costs nothing since the employees have already been paid, and it reveals every missing setting in one go.

Step 5: check the differences, line by line

Compare in this order, because each line depends on the previous one.

1. Gross salary. A difference here comes from a forgotten bonus, a mistransferred supplement, or a seniority bonus calculated on the wrong date.
2. Employee contributions. A difference almost always signals a misapplied ceiling, or an executive treated as a non-executive.
3. Income tax. Check the number of tax parts first, then the treatment of exempt transport allowances.
4. TRIMF. A difference by a factor of two comes from the number of TRIMF parts, which is 2 only for a married employee whose spouse has no income.
5. Net pay, which follows from the previous four.
6. Employer cost, to check the work accident rate and the IPM parameters.

A difference of a few francs on a payslip comes from rounding and should not worry you. A difference of several thousand francs always has an identifiable cause: find it, do not correct it by hand. A manual correction hides a wrong setting that will come back the following month.

Step 6: switch over and archive the old tool

Once the differences are explained, run the current month's payroll in the new tool, and only then. Before cutting off access to the old one:

• export all historical payslips as PDFs and file them in a dated folder. Payslips must remain accessible long after the subscription ends;
• export the raw employee data, in a format readable without the software;
• keep the filings already submitted to IPRES, CSS and the tax authority;
• note the exact switchover date, which will serve as a reference in the event of an inspection.

Only cancel the old subscription after checking these exports, and not on the day of the switchover.

The one-page checklist

Before

• [ ] Choose the switchover month, January if possible
• [ ] Retrieve complete employee records, seniority date included
• [ ] Retrieve the collective agreement, the work accident rate, the IPM parameters
• [ ] Retrieve the year's cumulative figures: taxable gross, tax, TRIMF
• [ ] Retrieve leave accrued and advances in progress
• [ ] Clean up: departed employees, duplicates, outdated tax parts

During

• [ ] Import employees and check a sample of records
• [ ] Enter the year's cumulative figures
• [ ] Replay the previous month exactly
• [ ] Compare gross, contributions, tax, TRIMF, net and employer cost
• [ ] Explain every difference beyond rounding

After

• [ ] Run the current month's payroll in the new tool
• [ ] Export the payslips and data from the old tool
• [ ] Archive the filings already submitted
• [ ] Cancel the old subscription once the exports are verified

Allow three to five working days for a headcount of around thirty, including the cleaning and the control month. At Izi Paie, employee records are imported from a CSV file and support with the transfer is included, whatever tool you are leaving.