Imperfectum and perfectum: 't' or 'd'?

How does the rule work with softketchup, ’t kofschip or ’t fokschaap? When does a part tense end on -te and -ten and when on -de and -den?

fietsen

fiets

Take the 1st person singular of the present

Take the letter just before en

Does the word softketchup contain this letter?

✘

✔

te
ten

ik/jij/u/hij/zij fiets
wij/jullie/zij fiets

ik heb gefiets

Exception

All irregular verbs.

Check on woordenlijst.org to verify if a verb is regular.

For the perfectionist

The letter 'x' should also be included with softketchup. There are only six verbs: detoxen, faxen, fixen, mixen, relaxen, and waxen.

So it is: ik detoxte, wij detoxten, and ik heb gedetoxt