Revenue have changed their system from the beginning of this year to e-stamping.
You still complete a SD4 but you now must also complete a SDR2 online. If you can't complete the SDR2 online, you have to request the form from Revenue. You then send SDR2 to Revenue and they may request SD4 thereafter.
You must also complete a stock transfer form, update the company registers and issue new certs / cancel old ones.
Also, you may want to consider is the person resigning a directorship. If so, you need to complete a B10 and send to Revenue. But please note, company must always have at least 2 directors and 1 secretary so you may need to appoint directors/ secretary. this can all be done on the same B10 form.