List what expires
Typically: training and competence cards for each person, first aid certificates, employer's liability and other insurance, PAT and other equipment tests, accreditations, vehicle documents and gas or electrical certificates.
Record it consistently
For each one: what it is, who or what it covers, the reference number, the issue and expiry dates, the issuer and the renewal cost. Scan or note where the original is kept.
Set a lead time
Renewals take time - a course has to be booked, a policy renewed, a test arranged. Look 30, 60 and 90 days ahead, not just at what's already expired.
Check by person and by asset
Before someone goes to site, check their cards. Before a tender, check the company's insurance and accreditations. One list, two views.